This work is an extension of studies into the mechanism of inhibition of a carbon steel in a 200 mg l-1 NaCl solution by a non-toxic multicomponent inhibitor used for the treatment of water in cooling circuits. The inhibitive formulation was composed of 50 mg l-1 fatty amines associated with 200 mg l-1 phosphonocarboxylic acid salts. The influence of flow was investigated by electrochemical impedance spectroscopy with a rotating disc electrode. The results were dependent on the experimental protocols used. The properties of the protective layers were dependent on the electrode rotation rate. The presence of two layers on the electrode surface with protective properties that depend on the electrode rotation rate allowed the non-monotonic variation of the corrosion current densities to be explained. This behavior was related to the influence of flow on the anodic kinetics.